<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <ul id="wrap"></ul>
</body>
</html>

<script>
var arr = [
  {
    name: 'Jack',
    age: 18
  },
  {
    name: 'Rose',
    age: 20
  },
  {
    name: 'Tom',
    age: 22
  }
];

// 将 arr “映射”至 <ul> 标签内

// 使得 <ul> 内部 的 内容为下例：

/* 
  <ul id="wrap">
    <li>
      <span>姓名：</span>
      <span>Jack</span>
    </li>
    <li>
      <span>年龄：</span>
      <span>18</span>
    </li>  
    ......
  </ul>

*/

</script>